Some antifriction bearings operate in extremely hostile environments. Typical are the bearings for the final drives of some track-laying vehicles, such as bulldozers. The bearings for a final drive reside between two housings, an inner and an outer housing, the former of which is bolted firmly to the frame of the vehicle, whereas the latter rotates and has a sprocket bolted to it. The sprocket drives an endless track. A so-called “duo-cone” seal that is fitted to the two housings adjacent to the inboard bearing isolates the bearings from water and from dirt and debris that are picked up by the track.
The typical duo cone seal (FIG. 1) for a final drive has two steel wear rings that contact each other along wear surfaces that lie perpendicular to the axis of rotation. One wear ring is fitted to the fixed inner housing with an O-ring between it and the housing, while the other wear ring is fitted to the rotatable outer housing with another O-ring between it and the outer housing. The O-rings not only support and position the wear rings in their respective housings, but also urge the two wear rings together so that they remain in contact along their wear surfaces.
Being fitted to the two housings, the duo cone seals are themselves considerably larger than the bearings that are between the two housings. This renders them more susceptible to deflections in the housings—and by reason of the high torque and forces applied to the housings, they deflect, sometimes to the extent that the wear rings separate at their wear surfaces. In short, the seals fail. The deflection may also cause the O-rings to slip and experience excessive wear.